The overvoltages here considered may be transients due, for example, to strokes of lightning or interference from nearby electrical components. A knowledge of their waveform, i.e. of the aforementioned criteria, is important for the installation of protective devices on such transmission lines and associated equipment.
The conventional way of analyzing the characteristics of overvoltage pulses involves their recordal on a tape or photographic film, or their visualization by an oscilloscope provided with pulse-storing circuitry. Recording or display devices used for this purpose are relatively expensive and require a practically noise-free power supply.